Abstract: 　AIM: To evaluate the 18 kDa antigen in diagnosis of human alveolar echinococcosis. METHODS: A total of 214 sera from patients with alveolar echinococcosis (AE, 33), cystic echinococcosis (CE, 69), cysticercosis (30) and healthy controls (82) were examined by Western blotting to detect the antibodies against 18 kDa antigen using both antigens from protoscoleces of E.granulosus (Eg) and E.multilocularis (Em). All the sera were tested simultaneously by ELISA to detect the antibodies against hydatid cystic fluid antigens of sheep as a comparison. RESULTS: The positive rate by ELISA was 93 9% in AE, 85 5% in CE, 50% in cysticercosis and 6 1% in healthy controls, respectively, suggesting a critical cross reaction and a certain degree of nonspecific reaction. The serum positive rates by Western blotting with the 18 kDa antigen of Eg and Em were 90 9% and 90 9% in AE, 10 1% and 13% in CE, 13 3% and 16 7% in cysticercosis, respectively. No positive was found in the sera from healthy controls. CONCLUSION: The 18 kDa antigen may be used in the differential diagnosis of AE from CE.

Key words: Alveolar echinococcosis, cystic echinococcosis, 18 kDa antigen, differential diagnosis, Western blotting